A cylinder having a close-off member mounted thereon is for example known from US patent publication U.S. Pat. No. 6,263,779. That document describes a method for coupling a close-off member, such as a close-off cover or a gland, for guiding a piston rod of a hydraulic damper of a vehicle suspension system, with a cylinder body of a damper of this type. The cylinder body has an open end with an edge and has on an inner surface a peripheral groove. This groove is formed set apart from the edge. The close-off member has an insert part having an outer surface which is introduced into the open end of the cylinder body. The close-off member also has a flange which extends in the radial direction and is located, after mounting of the close-off member, opposite the edge of the cylinder body. A second peripheral groove, wherein a spring ring is attached, is formed in the outer surface of the insert part for coupling the close-off member to the cylinder body in interaction with the first peripheral groove. A steel snap ring, which is divided in one location, is attached between the flange and an upper side of the edge of the cylinder body.
In this method known from U.S. Pat. No. 6,263,779, the close-off member is mounted in the cylinder body by feeding the insert part into the open end of the cylinder body and further displacing it therein until the two grooves oppose each other and the spring ring falls into the peripheral receiving space which is produced and couples both components to each other. As a result of the shape of both grooves, the spring ring is secured in a form-fitting manner in the receiving space when the close-off member is subsequently drawn out from the cylinder body somewhat. Afterwards, a steel snap ring having suitable dimensions is selected and placed between the flange and the edge of the cylinder body.
It is a drawback of this hydraulic cylinder known from U.S. Pat. No. 6,263,779 with a close-off member and this known method for coupling the close-off member that the placing of the steel snap ring takes place once the close-off member is already coupled to the cylinder body. The steel snap ring has to be attached afterwards, necessitating special equipment. In addition, owing to variations in dimensional tolerances of the various components, the distance between the underside of the flange and the edge of the cylinder body will vary and thus, at the moment of mounting of the steel snap ring, the correct dimension thereof will have to be selected in all cases. This is laborious and time-consuming.
A cylinder with a close-off member mounted thereon is also known from German patent document DE 44 33 649 A1. This document shows a metal locking ring which is attached in a peripheral groove on the outer surface of the close-off member, a separate metal spring ring being present between the locking ring and the front end of the cylinder in the mounted state of the close-off member.
DE 44 33 649 A1 has the same drawback as U.S. Pat. No. 6,263,779: the locking ring and the spring ring are placed only once the close-off member is already coupled to the cylinder body.
Furthermore, DE 44 33 649 A1 has the drawback that mounting of the close-off member is only possible by introducing the close-off member via a first open end in the cylinder into the interior thereof and subsequently by displacing the cylinder to the second open end of the cylinder to which the close-off member has to be fastened. This has the consequence that a close-off member can be mounted merely on one side of the cylinder.
In addition, it is a drawback both of U.S. Pat. No. 6,263,77 and of DE 44 33 649 A1 that dirt will be able to collect at the location of the steel snap ring. On the one hand, that can be dirt which is entrained at the moment when the snap ring is placed; on the other hand, that can be dirt which will be able to accumulate in the gaps which are present between the flange and the snap ring, between the edge and the snap ring, and in the region of the division seam in the steel snap ring. This is very disadvantageous, in particular when the hydraulic cylinder is used in a medical application, for example for a hydraulically adjustable hospital bed. Cleaning of the hydraulic cylinder is then impeded, as the dirt is situated in locations which are very difficult to reach and cannot be removed or can be removed only with difficulty.